Inflammation contributes at each stage in the development of clinically significant atherosclerosis. The initiation and[unreadable] progression of atherosclerosis is decreased in regions of steady flow associated with high laminar shear stress, compared to[unreadable] regions of turbulent and low flow. This finding has yielded the concept that "normal" flow is atheroprotective. Tissue[unreadable] culture and in vivo studies have shown that normal flow decreases oxidative stress by activating antioxidant mechanisms.[unreadable] The major hypothesis of this proposal is that normal flow promotes a reducing environment in endothelial cells that[unreadable] decreases inflammation and limits atherosclerosis. Our laboratory has focused on regulation of the mitogen activated[unreadable] protein kinases (MAPKs) by flow. MAPKs phosphorylate and activate transcription factors that induce expression of both[unreadable] pro- and anti-inflammatory molecules. In particular, apoptosis signal kinase-1 (ASK1) and its downstream effectors, c-Jun[unreadable] N-terminal kinase (JNK) and p38, are activated by almost all inflammatory cytokines. We believe that understanding the[unreadable] mechanisms by which flow regulates activation of ASKl-JNK-p38 will provide insight into the atheroprotective[unreadable] mechanisms induced by flow. We propose a model based on preliminary data that flow stimulates glucose 6-phosphate[unreadable] dehydrogenase (G6PD) which increases NADPH formation. NADPH increases the level of reduced glutathione (GSH)[unreadable] which maintains the key antioxidant molecules glutaredoxin (Grx) and thioredoxin (Trx) in reduced forms. Grx and Trx[unreadable] bind to ASK1 and keep ASK1 inactive. Flow also decreases expression of vitamin D3 upregulated protein (VDUP1) which[unreadable] is an endogenous inhibitor of Trx. To characterize the mechanisms by which flow inhibits ASK1 we will compare the[unreadable] effects of normal flow (shear stress = 12 dyn/cm2) and disturbed flow (low shear stress = 0.4 dyn/cm2 or oscillatory flow)[unreadable] on ASK1 activity basally and in response to tumor necrosis factor-alpha. Four aims are proposed. 1) To characterize the[unreadable] mechanisms by which flow activates G6PD based on mechanosensitive signaling pathways. 2) To determine how Trx[unreadable] inhibits ASK1 function based on the concept that flow maintains Trx in an active state. 3) To show that flow inhibits[unreadable] VDUP1 expression thereby increasing Trx activity and Trx binding to ASK 1. 4) To characterize the role of VDUP1 in[unreadable] atherosclerosis by evaluating the effect of VDUP 1 deficiency on the pathology of the LDL receptor deficient mouse. These[unreadable] studies should provide insight into mechanisms by which flow inhibits arterial inflammation and facilitate development of[unreadable] new therapeutic approaches to limit atherosclerosis.